1. Field of the Invention
The invention relates to clutches, particularly for automatically operated automotive transmissions which have positive acting clutch components as well as non-positive acting clutch components. Multiplate clutches with hydraulic operation are generally known in the field of automatic transmissions. These clutches may include non-positive acting clutch components and require, as a function of the torque, a correspondingly high number of plates, resulting in drag losses and large construction space and the same are also expensive. Hydraulically operated jaw-type clutches, which are operated by means of an external hydraulic cylinder, are also known. These hydraulically operated jaw-type clutches have the disadvantage that they can be opened and closed only when they are unloaded. As a rule, the shift gearing of these jaw-type clutches has a drive face, which is perpendicular to the force applied along the circumference or which may even be undercut counter to the direction of shift in order to ensure safety against opening.
U.S. Pat. No. 3,679,032 discloses a clutch design which is similar to the clutches of the present invention in that it provides for fluid pressure pistons to shift the clutch rings for closing of the clutch. This prior art clutch is strictly a positive acting clutch having a straight clutch profile with the disadvantage that the clutch, after removal of the fluid shift pressure from the pressure piston, opens only after the clutch is unloaded and is free from torque.
German Offenlengungsschrift 1 575 802 discloses an electromagnetic clutch which has shift gearing that is similar to the subject matter of the present invention in that it produces an axial torque-dependent component of force. As is well known, however, these electromagnetic clutches occupy large construction spaces and therefore, for this and for other reasons having to do with the necessity for electrical supply and connections and the like, are unsuitable for use in motor vehicles.
The object of the invention is to provide a clutch which preferably serves for the range shifting of continuously variable transmissions and overcomes their drawbacks. It must be possible for the clutch to be disengaged when it is under load and it must be compact and short, especially in the axial direction.
Clutches embodying the invention offer the further advantages that they (1) can be economically employed and can be produced at low cost, (2) permit a small, compact mode of construction for several clutches in a clutch assembly, (3) are free from drag losses unlike the multiplate clutches of prior art, thus contributing toward improving the overall efficiency, (4) can be operated when synchronized and under load or at relatively low rotational speeds depending on the requirements of the range shifts in continuously variable transmissions, and (5) can be opened when under load.
These objects are achieved by the provision of a clutch mechanism which comprises an elongated shaft mounted for rotation about its longitudinal axis; a clutch carrier mounted on said shaft for rotation therewith in a fixed axial position; and first and second clutch assemblies, each of which include a movable ring and a mating ring. The rings of each assembly have facing interengageable clutch surfaces and the movable rings are mounted on the carrier for movement along respective axial paths with their respective clutch surfaces facing in the same axial direction. The mating rings are respectively positioned on the paths along which the movable rings move with their respective clutch surfaces facing in the opposite axial direction from the direction that the surfaces of the movable rings face. The mechanism also includes means carried by the carrier for moving the movable rings independently toward their respective mating rings. Preferably, the facing interengageable clutch surfaces of at least one of the assemblies comprise clutch profiles which are configured to assist in moving the rings apart under load. And preferably the means for moving the movable rings independently comprises a fluid actuated piston element for each movable ring. Further advantageous embodiments will becomes apparent from the description which follows.